The reason they would have to be blown in the middle is that all of the film shot at different angles show the collapse occuring at the approximate site of the plane crashes.
The lower portion of the building is fully intact as the upper floors pancake down on them. My guess is that ground zero absorbed the same amount of energy as a small tactical nuclear device.
No, I don't mean to imply that buildings are not collapsed from the bottom.
In reality, TV commentators make a big deal about the science behind demolition of buildings, when in reality it is actually fairly easy if you have studied the process.
The idea is the blow out load-bearing structures using timing between each structure so that the building collapses in on itself. The amount and placement comes from "rule of thumb" rules that were developed and improved upon since WWII.
My point is (on the amount of explosives) that the people would have to bring in a fairly large amount, which would be detectable. The Trade-Centers have been carefully monitored since the first attack from the basement parking. Notice that when it occurred they were also trying to bring down the building, but miserably failed. There was; however, more damage than it looked like since the bomb blew our floors up through about eight stories.
Partially because of the tubular construction however, a truck load of ANFO failed to bring the big building down.
Yes, we could be talking past each other. I was at church for the last few hours.
On the lighter side, have you ever seen the buildings that failed to fall when they were blown? One fell over onto another building and just leaned there. I don't have any point to make concerning the issue here, but just thought it was an interesting film.
It does make for a very dangerous situation because you have buildings with obvious damage to the major load-bearing structures and to re-enter and try to re-place charges is not only very dangerous, but also difficult to determine exactly where the pressures lie.
In all seriousness, look closely at any picture or film of the WTC towers. The puffs of smoke that people have claimed were explosives are actually concrete floors collapsing in on themselves. Explosives mounted in the building would have had a slightly faster appearance, and also the amount used would not have blown out so much debris.
The beginning of each collapse was at the exact point to be expected and that is where the weakness from the plane and fuel heat finally caused the hangers mounting the concrete floors to the outside load-bearing wall to let go.
There was a moment on each building that it appeared the top might topple, but the heavy weight of the pancaking concrete overrode the skewing movement and brought them straight down.
If you ever watch a building that is demolished, you will notice that usually dynamite is used and it is drilled and placed into the pillars or areas to cut. Sometimes, "cutting" cord is used. This includes either a long shaped charge of Composition 4 (C4) which can cut through a steel beam; or another type of cutting cord which uses two rows of explosives about a half-inch apart. The detonation moves down the cord from the blasting cap or primer/detonator. Since the detonation travels about 7000 meters per second (7 KM per second), they run down the cord almost instantaneously to the human eye. But, what happens is the explosives move at the same speed creating a tremendous shock-wave in the air. The shock-waves from the two explosives collide and cause a super-shock which knifes through the steel like butter. There is nothing secret about these methods, they are all used commercially. The cutting ribbon is often used under the ocean to cut off pipes near the ocean floor when moving a drilling-platform.
Then there is one final way, which is probably used most often by building engineers in the military to clear trees or buildings for construction and that is a flat sheet of C4 wrapped around the item to be cut.
But, even with all of these methods it would take a LOT of explosives to cover all of the load-bearing members of those huge buildings. Especially since the external wall was used like a pipe carrying most of the weight.
To carry this amount of explosives into the building would be next to impossible without detection.
Besides, nothing works better for the terrorists that a huge airliner fully fueled. I think; however, the pilot that flew into the Pentagon found out just how hard it is to hit a LOW target due to the ground effect, but he didn't have very long to think about his discovery.
